Can you show the exact steps you're taking to build the U-Boot image, put it into NAND flash, and boot it? What exact SHA1 of the U-Boot git tree are you using, and are there any local changes?
Have you tried "run nandboot" to soft-boot into NAND rather than switches?
Where did you get the U-Boot image that you're running out of NOR? What happens if you build a new P2020RDB-PC image and flash it into NOR (make sure you have a way to recover your old image via JTAG, and/or use the alternate flash bank)?